Icons play an extremely important role in the visual of an operating system of computers. The icons may represent a document, a program, a web page, or a command. Besides, it is possible to execute a command, open a certain type of document, or operate a certain type of application with the use of icons. As an access for initiating an application program in the operating system, the icons are convenience and efficient. Generally, the application program corresponding to an icon may be executed only by clicking or double clicking the icon.
The sizes of icons required by different operating systems are different from each other. In order to facilitate a user's identification, the same picture is often used as an icon of the same application program for a long time. Generally, the icons are static pictures with fixed resolutions and without multi-media effects.